[babel] noweb reference with default values

[Andreas Leha <andreas.leha@med.uni-goettingen.de>]

Hi all,

I'd like to hear your ideas on how to include noweb references to code
blocks in a way that the default values are used as parameter values.

Here is a little example:

#+PROPERTY: header-args:R :session *testR*

The background is that I like to use Org mode table to record small data.

#+name: datatable
| A |  B |
|---+----|
| 1 | 10 |
| 2 | 20 |

Usually I want to pre-process and/or convert such data.

#+name: read_datatable
#+header: :var datatable=datatable
#+begin_src R :results none
  datatable$B <- 10 * datatable$B 
#+end_src

Later I would like to use that data in larger (R-) code blocks.  I'd
like such code blocks to DWIM:

#+name: some_code
#+begin_src R :noweb yes :results graphics :file testplot.png
  <<read_datatable>>
  plot(datatable$A, datatable$B)
#+end_src

But they do not: They are not stand alone and do not execute -- unless I
executed `read_datatable' manually/by chance upfront.



My current solution is to export the table to csv and read that csv in
`read_datatable'.

If the result of `read_datatable' is a single table again (as in this
MWE) I usually return that to Org mode which works ok.  But often the
result is more complex than that.

I see two ways to go:
- I could serialize more complex objects to disk and return a file name.
  But I'd prefer to not go through disk.
- I could pass the same arguments as to `read_datatable' also to
  `some_code'.  But that is duplication and becomes quite convoluted in
  the case of several noweb references with several arguments each.

Any ideas how to do that better?

Thanks,
Andreas